1. Field of the Invention
The present invention relates to a control apparatus for a vibration actuator.
2. Description of the Related Art
A conventional control apparatus for controlling a vibration actuator is arranged to set a driving signal to be applied to a vibrating member (i.e., a stator) of the actuator to be zero when a movable member (i.e., a rotor) of the actuator is stopped, as disclosed in, e.g., Japanese Laid-Open Patent Application No. 63-18974.
In the above-mentioned prior art, the actuator does not consume any electric power while the actuator is stopped. However, in the control apparatus of the actuator, since a driving circuit connected to the vibrating member, a sensor for detecting the instantaneous position of the movable member, a position detection circuit, and the like are energized, the following problems are posed. That is, (i) electric power consumption is increased in a use with a long stop time of the movable member, and electric power utilization efficiency is lowered, and (ii) since the control apparatus generates a large amount of heat, such heat is not preferable for an electronic circuit.
In order to solve these problems, when the actuator is stopped, energization to the control apparatus may also be stopped. However, when the conventional control apparatus adopts such an arrangement, the following problems are posed. That is, (i) since position information obtained when the movable member was stopped is lost, control precision is lowered after the control apparatus is restarted, and (ii) the movable member undesirably moves when a power supply is turned on/off.
Furthermore, since a conventional actuator device starts its driving operation immediately after a power supply is turned on, the actuator device may be undesirably driven in an unstable state of a power supply circuit.